For many years, communications and word processing equipment, such as modems, multiplexers, terminals, computers, printers, and data PBXs have employed serial ports having a variety of connector types including D-subminiature construction for connecting to similarly configured connectors on the end of a relatively heavy gauge multi-conductor or coaxial cable. Recently, newer commercial building wiring standards, such as the EIA568 standard have been adopted by the Telecommunications Industry Association and the Electronics Industry Association (TIA/EIA), now require twisted-pair network systems.
Twisted-pair technology is therefore quickly challenging the traditional dominance of co-axial cabling in a wide range of computer and data communication applications, and has been established to be more flexible and less expensive than other wiring products. Twisted-pair cables are typically terminated with miniature modular plugs and jacks of the quick-connect-and-disconnect variety designed originally for use with telephone equipment. The combination of a multi-conductor cable terminated by one or more modular plugs is commonly referred to as a "cordset".
In order to satisfactorily achieve a connection between existing D-subminiature outlets on commercial communication and data processing equipment and these increasingly popular modular plugs of twisted-pair networks, modular adapters have been developed. These commercial adapters often include a D-subminiature male or female connector carefully wired to a RJ-jack.
Although modular adapters have bridged the technology gap between existing D-subminiature serial ports and twisted-pair networks, problems have arisen during high speed data processing. When processing speeds exceed about 10 megabytes/second, the incidence of electromagnetic interference and noise increases substantially in unshielded cables. In response, the art has employed extremely thin layers of conductive material bonded to the outer surface of the twisted-pair insulated wire to shield the transmission from electromagnetic and electrostatic charges. Such shielded cables are then terminated in a normal modular plug, resulting in a shielded cordset.
A shielded cordset is typically connected through one of the contact terminals of the modular plug to a source of ground potential external to the connection. This can be made by grounding the solder post end of one of the connections of the mating modular jack. This technique for grounding shielded cordsets unfortunately has been known to result in an "antenna-effect" caused by the passage of the high frequency signals along the lengthy grounded conductors. Additionally, electrostatic voltage created along the shielding may arc into adjacent signal conductors in looking for ground. This may result in unintended damage to expensive low voltage circuitry.
In an effort to overcome the short comings of narrow path, ground connections made to solder post ends, the art has also experimented with ground conductors extending outside the insulating housing of modular jacks, as disclosed in Hall, U.S. Pat. No. 4,732,568 ("the '568 patent"), which is hereby incorporated by reference. These ground conductors typically include a stamped metal casing having a surface area substantially greater than that of the ground spring contact, or other conductors within the modular connector. Typically, this ground conductor is terminated with a ring terminal, spade lug, or solder post.
Unfortunately, shielded, twisted-pair cabling looses its effectiveness when connected to an unshielded modular adapter. As yet, the art has not provided an adapter configuration which both meets the needs of standard modularity, while simultaneously providing a ground voltage to completely protect the wiring network from inductive and electrostatic effects.